Stent for bifurcation, a system for intravascular implantation of the stent for bifurcation and a method of implantation of the stent for bifurcation

ABSTRACT

A stent for bifurcation, including two cylindrical parts: a distal part ( 1.1 ) of smaller diameter and a proximal part ( 1.2 ) of greater diameter, connected by two—arranged as opposite—longitudinal connectors ( 1.3 ) having length (L 1 ) of 0.5 to 8 mm and forming a cell of the stent having an enlarged surface area ( 1.4 ), the connectors having a curvilinear shape, in particular a sinusoidal shape.

Object of the invention is a stent for bifurcation and a system for intravascular implantation of the stent for bifurcation.

The state-of-the art systems for intravascular implantation of stents for bifurcation, utilizing various structural solutions at implantation of the stent often marker band about injuries, especially at ramifications of arteries. The most frequent problems at implantation of the stent for bifurcation include partial or complete closure of a side branch of arteries, contraction of side branch of artery, dissection at bifurcation of vessels, a decrease in a cross section of a side branch of artery as a result of marker band of lumen with struts of an implanted stent, and occurrence of thrombosis foci.

To avoid such situations, at present either one stent per each branch is implanted while using separate systems for intravascular implantation for each of the implanted stents or one forked stent, mounted on the complicated system, is implanted.

Operations of intravascular implantation of stents for bifurcation using state-of-the-art methods are extremely complicated to implement and burdened with very high probability of various post-operational complications in arteries with stents. They must be carried out in surgeries provided with very modern equipment. Furthermore, operators carrying out the implantation are required to have high skills and much experience.

Accordingly, there is a demand for new, more effective structural solutions for stent for bifurcation and systems for intravascular implantation of such stents, in order to facilitate implantation at a bifurcation site even by less experienced operators and to provide higher safety and efficacy of operation.

Aim of the present invention, is to increase efficacy and to facilitate implantation procedure, thus increasing safety of operation and promoting more wide use of stents and developing more universal construction of stent extendable on a balloon, which allows its implantation in vessels having different shapes and sizes and of different mutual arrangement of a branch with respect to the main vessel.

From international application WO0174273A1 a self-expanding stent made of materials, such as e.g. nickel and titanium alloys, consisting of two segments—proximal and distal is known, one of them having greater diameter, and the segments being connected by at least one longitudinal connector. That connector (or several connectors located close to each other) is rectilinear and is located only at one side of the stent, so that at the other side between two segments of the stent a free space is formed. The connector of the stent upon implanting in blood vessel adheres to an internal wall of the vessel and it bends in such a way that segments of the stent change their mutual position (there is an angle between them), and free space between them is freely increased.

A stent for bifurcation of the invention, consists of two cylindrical parts: a distal part of smaller diameter and a proximal part of greater diameter, connected by two—arranged as opposite—longitudinal connectors having length of 0.5 to 8 mm, that form a cell of the stent having an enlarged surface area, the connectors having a curvilinear shape, in particular a sinusoidal shape.

Preferably, a ratio of the distal part diameter to the proximal part diameter of the stent is within the limits of 1.0:1.1 to 1.0:2.0.

A system for intravascular implantation of the stent for bifurcation, consisting of the proximal part and the distal part including an external tube, an internal tube, and a profiled balloon, according to the invention, is characterized in that—in the distal part of the system—on the internal tube marked with three marker bands, visible at X-rays, there is a profiled balloon fastened with the proximal part to the external surface of the external tube and with the distal part—to the external surface of the internal tube, and on the profiled balloon, a stent for bifurcation defined in claim 1, as presented above, is clamped in a detachable way, the profiled balloon consisting of three non-separable parts—a distal part, of smaller diameter, a proximal part, of greater diameter, and a medial part having length of 0.5 to 8 mm located between the distal part and the proximal part, position of the medial marker band coinciding with the proximal edge of the distal part of the stent clamped on the balloon.

Preferably, a ratio of the distal part diameter to the proximal part diameter of the profiled balloon is within the limits of 1.0: 1.1 to 1.0: 2.0.

Between the long edges of the distal part of the profiled balloon and the edge of the medial part of the profiled balloon there is an angle θ that lies within the limits of 15° to 65°.

Upon clamping the stent for bifurcation on the profiled balloon in a separable way, a cell having an enlarged surface area of the stent for bifurcation, coincides with the medial part of the profiled balloon.

Method of introducing and positioning the stent for bifurcation by means of an intravascular system including the stent of the invention, is characterized in that a guide wire is introduced to a main branch of a vessel at bifurcation site, after which, a system defined in claim 3, as presented above, is introduced into the bifurcation site, including the stent defined in claim 1, as presented above, a medial marker band visible at X-rays signaling a position of the proximal edge of the distal part of the stent clamped on the balloon being precisely positioned at a site, where there is a groin of the vessel, such that the distal part of the stent is situated behind a fork of the artery, in a main branch, whereas the proximal part of the stent is situated before the fork of the artery, and the medial part of the stent , with a cell of the stent having special, enlarged surface area, is located in the lumen of the side branch of the vessel, and then liquid under pressure from 6 to 20 atm is introduced to the balloon, the stent is implanted, then, the fluid is removed from the balloon and the system and the guide wire are withdrawn.

On the internal tube of the system for intravascular implantation of the stent for bifurcation, three marker bands visible at X-rays, are fastened, in such a way, that a first marker band coincides with a beginning of long edges of the proximal part of the profiled balloon, a second marker band coincides with a beginning of long edges of the distal part of the profiled balloon, whereas a third marker band coincides with an ending of long edges of the distal part of the profiled balloon.

The stent for bifurcation is suitably clamped in a detachable way on the profiled balloon.

The stent for bifurcation and the system for its implantation in an embodiment example is shown on a drawing, in which FIG. 1 shows a view of the stent for bifurcation with a visible cell of the stent having enlarged surface area, in FIG. 2 the balloon constituting an element of the system for stent implantation is shown, in FIG. 3—a view of the distal part of the system for intravascular implantation of the stent for bifurcation and its location in a branch of artery, being a site of implantation of the stent is shown, in FIG. 4 the stent located in the vessel at its bifurcation site upon withdrawal of the system, and in FIGS. 5A, 5B, 5C—as a matter of example—positions of the distal part and the proximal of the stent upon its positioning in the vessel are shown.

A special, profiled structure of the stent for bifurcation allows such positioning of the system for intravascular implantation of the stent for bifurcation during implantation of the stent for bifurcation that the distal part of the stent is positioned behind the fork of the vessel, in a more narrow part of the vessel, the proximal part of the stent for bifurcation is positioned before the fork of the vessel, and the medial part of the stent, with connectors of the stent, forming at the same time the cell of the stent having special, enlarged surface area, being positioned precisely in a lumen of the side branch, thereby preventing from blocking blood flow through the side branch of the artery.

Two opposite connectors assure that both parts of the stent are kept at a suitable distance from each other, but at the same time the connectors allow, within a defined range, free adjusting to an anatomical shape of vessels. Both parts of the stent upon implantation are supported in an uniform way by the two connectors located symmetrically on two sides of the stent.

Connectors are located longitudinally with respect to the stent and are curved e.g. have a sinusoidal shape, a wavy shape, a shape of letter “S” or a double “S” shape or an accordion shape or are slightly twisted, like an extended fragment of a helix. Such shapes of connectors cause that—depending on a structure of the vessel, where the stent will be implanted—they may be easily expanded or clamped, so that a primary distance between the proximal part and the distal part of the stent will be increased or decreased. A distance between the parts of the stent upon its implanting at the side of the first connector and at the side of the second connector may be different, as it is shown in FIGS. 5B and 5C. In that case, the parts of the stent are positioned to each other in such a way that there is an angle between them. The connectors also make it possible to carry out a slight shift of the proximal part and the distal part of the stent with respect to the longitudinal axis of the stent. Primarily both parts of the stent are arranged in such a way that their symmetry axes overlap, as it is shown in FIG. 1. No matter how parts of the stent will be arranged with respect to each other upon implanting, the two opposite connectors limit freedom of movement of the stent at its implantation and do not enable unrestricted movement of the distal part and the proximal part of the stent.

Location of a system of three marker bands well visible at X-rays on the internal tube provides precise positioning and visibility of the stent for bifurcation during its implantation in vessels. The stent for bifurcation is tightened in a separable way on the profiled balloon in such a way that a cell having an enlarged surface area of the stent for bifurcation coincides with the medial part of the profiled balloon. Marker 7 coincides with the proximal edge of the distal part of the stent clamped on the balloon, and during implantation of the stent, marker 7 must coincide in the vessel with a beginning of the carina tip of the vessel. A specific shape of the profiled balloon prevents from shifting the carina tip of the vessel during implantation of the stent for bifurcation, thus preventing from blocking blood flow through the side branch of the artery.

The stent expandable on the balloon of the invention is entirely made of typical, known materials used for such purposes, preferably of stainless steel 316L or alloy L605.

The stent for bifurcation 1 of the invention, consists of two cylindrical segments—of the distal part, of smaller diameter 1.1 and of the proximal part, of greater diameter 1.2, connected by two connectors 1.3 having length L1, forming the cell of the stent having an enlarged surface area 1.4. The distal part of the stent may be longer or shorter than the proximal part of the stent. Both parts of the stent may also be approximately equal to each other. Prior to implantation both parts of the stent are positioned coaxially. The connectors, with which the stent is equipped, are arranged as opposite—i.e. on a circumference of the stent they are located 180° apart. A distance between the proximal part and the distal part of the stent may have length from 0.5 to 8 mm, e.g. from 0.5 to 3 mm or from 2 to 4 mm, or from 3 to 8 mm. Preferably both connectors have equal length. Preferably connectors are not rectilinear but are of a curved shape, e.g. a sinusoidal shape.

The system for intravascular implantation of the stent for bifurcation of the invention in its distal part consists of the profiled balloon 2 fastened to the system in that way that the proximal part 2.2 of the profiled balloon 2 is fastened to the external surface of the external tube 4 of the system, and the distal part 2.1 of the profiled balloon 2 is fastened to the external surface of the internal tube 5 of the system.

The profiled balloon 2 consists of three non-separable parts: the distal part, of smaller diameter 2.1, the proximal part, of greater diameter 2.2, and the medial part 2.3 of a defined length, located between the distal part 2.1 and the proximal part 2.2. The distal part of the balloon may be longer or shorter than the proximal part of the balloon. Both parts of the balloon may also be approximately equal. The medial part of the balloon is adjusted to a distance between the distal part and the proximal part of the stent and may have length from 0.5 to 8 mm, for example from 0.5 to 3 mm or from 2 to 4 mm, or from 3 to 8 mm.

Between long edges of the distal part 2.1 and an edge of the medial part 2.3 of the profiled balloon 2 there is an angle Θ. The stent for bifurcation 1 is clamped in a separable way on the profiled balloon 2 in such a way that the cell of the stent having an enlarged surface area 1.4 of the stent for bifurcation 1 coincides with the medial part 2.3 of the profiled balloon 2, the distal part of the stent 1.1 is mounted on the distal part of the balloon 2.1 and the proximal part of the stent 1.2 is mounted on the proximal part of the balloon 2.2.

On the internal tube 5 of the system for intravascular implantation of the stent for bifurcation at least one marker band 7 is fastened, preferably three marker bands 6, 7, 8, visible at X-rays, in such a way, that the marker band 6 coincides with a beginning of long edges of the proximal part 2.2 of the profiled balloon 2, the marker band 7 coincides with a beginning of long edges of the distal part 2.1 of the profiled balloon 2, and the marker band 8 coincides with an ending of long edges of the distal part 2.1 of the profiled balloon 2. The stent is tightened in a separable way on the balloon of the system in such a way that the marker band 6 coincides with the proximal edge of the stent 1, the marker band 8 coincides with the distal edge of the stent 1, and the marker band 7 coincides with the proximal edge of the distal part 1.1 of the stent, in other words the marker band 7 coincides with that edge of the distal part of the stent, which is situated at the side of the cell of the stent having an enlarged surface area 1.4.

The system for intravascular implantation of the stent of the invention is introduced into body in that way, that the guide wire P2 is delivered to the bifurcation site that is positioned in the main branch of the artery.

Then, the system for intravascular implantation of a stent of the invention is introduced on the guide wire P2.

The internal tube 5 of the system for intravascular implantation of the stent is put onto the guide wire P2.

Then, while shifting the entire system for intravascular implantation of the stent on the guide wire P2, controlling at the same time position of the three marker bands 6, 7, 8 by X-rays, the stent for bifurcation 1 with the profiled balloon 2 is very precisely positioned at the bifurcation site: the system is introduced on the guide wire P2 into the main branch of the artery, so that the marker band 7 would be at the same height, where the carina tip of the vessel is situated. By means of control of position of the marker 7 it is possible to position proximal edges of the distal part of the stent 1 precisely in one line with the carina tip of the vessel.

Such introduction of the system for intravascular implantation of the stent for bifurcation results in that the distal part 1.1 of the stent for bifurcation is situated behind the fork of the artery, in the main branch, the proximal part 1.2 of the stent for bifurcation is situated before the fork of the artery, and the medial part of the stent, with the cell of the stent having a special, enlarged surface area 1.4, is positioned in a lumen of the side branch.

Then, a fluid under pressure of 6 to 20 atm is introduced to the profiled balloon 2, which causes expanding of the profiled balloon 2, thus opening the stent for bifurcation 1. The open stent for bifurcation 1 widens lumen of the vessel, thus eliminating contraction.

Upon total opening of the stent for bifurcation 1, its medial part, with the cell of the stent having a special, enlarged surface area 1.4, is positioned precisely in a lumen of the side branch, which allows free blood flow through the side branch of the artery.

Then, the fluid is removed from the profiled balloon 2, the whole system with the empty profiled balloon 2 is withdrawn from blood circulation system. At the end, the guide wire P2 is withdrawn. The open stent for bifurcation 1 remains at the site, where there was contraction of the artery, thus causing its permanent widening. 

1. A stent for bifurcation, comprising two cylindrical parts: a distal part of smaller diameter and a proximal part of greater diameter, connected by two longitudinal connectors, arranged as opposite, having a length of 0.5 to 8 mm and forming a cell of the stent having an enlarged surface area, wherein the connectors have a curvilinear shape, in particular a sinusoidal shape.
 2. A stent of claim 1, wherein a ratio of the distal part diameter to the proximal part diameter of the stent is within the limits of 1.0:1.1 to 1.0:2.0.
 3. A system for intravascular implantation of the stent for bifurcation, comprising: a proximal part and a distal part including an external tube, an internal tube and a profiled balloon, wherein in the distal part of the system, on the internal tube marked with three marker bands, visible at X-rays, there is the profiled balloon fastened with a proximal part to the external surface of the external tube and with a distal part—to the external surface of the internal tube; and the stent for bifurcation of claim 1 is clamped on the profiled balloon in a detachable way, the profiled balloon including three non-separable parts—the distal part, of smaller diameter, the proximal part, of greater diameter, and a medial part having length from 0.5 to 8 mm, located between the distal part and the proximal part, position of the marker band coinciding with the proximal edge of the distal part of the stent clamped on the balloon.
 4. A system of claim 3, wherein a ratio of the distal part diameter to the proximal part diameter of the profiled balloon is within the limits of 1.0: 1.1 to 1.0: 2.0.
 5. A system of claim 3, wherein between long edges of the distal part of the profiled balloon and an edge of the medial part of the profiled balloon there is an angle θ that lies within the limits of 15° to 65°.
 6. A system of claim 3, wherein upon clamping the stent for bifurcation in a separable way on the profiled balloon, the cell having an enlarged surface area of the stent for bifurcation, coincides with the medial part of the profiled balloon.
 7. A method of introducing and positioning the stent for bifurcation by means of the intravascular system including such the stent, wherein the guide wire is introduced to the main branch of the vessel at bifurcation site, upon which at bifurcation site, the system defined in claim 3 including the stent defined in claim 1 is introduced, the marker band visible at X-rays signaling the position of edges of the proximal distal part of the stent clamped on the balloon being positioned precisely at a site, where a carina tip of the vessel is situated, so that the distal part of the stent is situated behind a fork of the artery, in the main branch, the proximal part of the stent is situated before the fork of an artery, and the medial part of the stent, with the cell of the stent having a special, enlarged surface area, being positioned in a lumen of the side branch of the vessel, and then fluid under pressure of 6 to 20 atm is introduced to the balloon, the stent is implanted, the fluid is removed from the balloon and the system and the guide wire are withdrawn. 